High resolution microscopy is used in research and development, quality assurance and production in diverse fields such as material science, life science, the semiconductor industry and the food industry.
Optical microscopy, dating back to the seventeenth century, has reached a brick wall defined by the wavelength of deep Ultra Violet photons, giving a finest resolution of about 80 nm. The popularity of optical microscopy stems from its relative low price, ease of use and the variety of imaging environmental parameters—all translated to availability.
Scanning electron microscopy provides a much finer resolution (down to a few nanometers), but in order to achieve this high resolution the inspected object must be placed in a vacuum environment.
Determining a Working Distance
In non-vacuum Scanning Electron Microscopes, the distance between the object and the microscope (also referred to as “working distance”) is of the order of a few to tens microns. Knowing the exact working distance is important for resolution and contrast optimization, for safe imaging of an object without contacting the optics of the microscope, for reducing contamination generated by such a contact, and for generating a focused image by setting the focusing lens accordingly. There is a growing need to provide a fast and accurate method and system for determining the working distance.
Reducing the Working Distance
The working distance between the object and the optics of the microscope should be as small as possible but large enough to prevent the object from contacting the microscope or otherwise contaminating the microscope. There is a growing need to provide an optimal trade off between the working distance and contamination hazards.